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1500 questions
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How to calculate flow rate of water through a pipe?
If a water pipe is 15 mm diameter and the water pressure is 3 bar, assuming the pipe is open ended, is it possible to calculate the flow rate or water velocity in the pipe?
Most of the calculations I have found appear to need 2 of these: diameter,…
Richard
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Why do we even use engineering stress?
Surprisingly this hasn't been asked before, so I must be missing something simple.
We use engineering stress and engineering strain in this eq. Stress = (Young's modulus) × (strain). This eq. is used in analysis of bending beams, twisting shafts…
Jessica
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What kind of math do engineers really use?
I am from the mathematics StackExchange section, many of my students are engineering students at University. I was wondering what kind of calculus do you real engineers use? I have known two engineers. One from airplane design and another from…
Nicolas Bourbaki
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Why are hyperboloid towers not popular anymore?
Hyperboloid towers were very popular in the end of 19th and the first half of 20th centuries - water towers, powerline anchor towers, sometimes tall radio towers were built using this design. The claimed advantage is using less steel compared to…
sharptooth
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What unit of weight is that?
Recently I was weighting stuff with my dad and as I was playing with one of the old 2 kg weights I felt with my fingers number "5". After cleaning and upon further inspection it turned out the writing on the weight says "5Φ". We checked and it…
elementiro
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15
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What is this small rotating part from a cell phone?
What is this tiny rotating piece of hardware that I found inside my Samsung GE1202? It has E9C written in blue on it.
PyRoss
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What is this large steel structure used in excavation?
I keep seeing these large rectangular structures on job sites they put in the ground.
I'm guessing something for strengthening the surface structures?
v15
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Can I use a ultrasound sensor to measure water level?
If I use an ultrasonic sensor will it detect the water level?
I was thinking about a product to read water level on water boxes (common in Brazil). I researched about instrumentation for this measure, and I think that an ultrasonic sensor is the…
Henrique Oliveira
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How do I size metal plates to get the correct dimensions after folding?
I am designing a metal plate that will be laser-cut (or machine-cut) and then folded. I want to know how to size the pre-folded plate in order to get the right dimensions after folding.
My actual part is not exactly like this (I simplified it for…
jhabbott
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Quantifying inertia on the electricity grid
A lot of discussion about the modernisation of electricity systems is about "inertia". This is usually a qualitative discussion about how turbines (in hydro, coal & gas plants) with lots of kinetic energy in the form of angular momentum and fast…
410 gone
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Purpose of spheres and fins on submarine propeller
On a recently launched Russian diesel-electric submarine, the rear propeller has two distinct features. You can see spheres at the base of every propeller blade:
Also, the trailing edge of the shaft has four adjoining fins in line with the axis of…
Rupert Reckless
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4 answers
How should the public raise questions about unsafe structures in the United States?
In a program on NPR that I was listening to, there was a bit about a bridge that from the description sounded to a layman as unsound and is still in use. The program described it as an old wooden railway (and I'm aware that has its own set of…
user348
14
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5 answers
Are there any materials known to be sound-insulating but thermally-conductive?
Are there any materials known to be sound-insulating as well as thermally-conductive?
Cost is not an overriding concern, but preferably costing "reasonable amounts" and much less than national defense spending levels.
This is a thought experiment…
Jimmy Hoffa
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Why is Mach 0.3 the threshold separating compressible and incompressible flow?
I've read that Mach 0.3 is pretty much the upper limit for treating air as an incompressible fluid. The sources I've read seem to treat this as a given, without proof or justification.
Why is this the limit? Is there a mathematical justification…
Paul
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What are some cost-effective metal substances that can wet glass?
A highly desirable property of metals like gallium and indium is that they are able to wet glass.
Normally, as metals, they wouldn't be able to form an airtight seal when in contact with glass. But they are able to do so, and they can be used in…
APerson
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